For many communications applications, it is important that the communications system offer secure transport of messages. Information content is often sensitive and therefore must be protected from unintended “eaves dropping” and subsequent unauthorized use.
Preventing the unwanted use of transmissions represents a special challenge for wireless communications systems. Potentially, any wireless communications device can intercept and decode the wireless transmissions of any other device that is within range, and it is extremely difficult to detect unintended reception. In addition, determining if a station is a legitimate participant of a wireless network is not always straightforward. For example, a wireless transmission within an office might be received by a competitor sitting in a parking lot adjacent to the office.
Therefore, it is desirable if not essential that wireless communication systems implement security protection mechanisms. When considering such mechanisms, it is both desirable to maximize the level of protection while at the same time minimize potential negative impacts, such as increased cost and complexity of the devices, decreased throughput, and inconvenience to the user. Multiple mechanisms may be used in concert to provide improved levels of protection.
Various mechanisms have been used to protect wireless networks. In some cases, protection mechanisms are not implemented due to the cost incurred and inconvenience to the user because of the need to configure the system with encryption keys or other information used to authenticate devices.
Some wireless communication systems utilize identifiers which must be supplied by devices desiring to participate in a network. Specialized network coordinating “base station” devices authenticate requesting devices based on reception of the correct identifier. Such systems are simple to implement but provide weak protection because the identifier when transmitted to the “base station” is not protected and can therefore be easily intercepted.
Other wireless systems utilize secret encryption key(s). Keys are not transmitted over the wireless network. Instead, devices demonstrate knowledge of the key(s) by encrypting test messages. Coordinating base stations receiving a correctly encrypted test message authenticate the device transmitting the message. Such systems when correctly designed provide strong protection, but are relatively complex.
Some wireless communications systems utilize encryption keys together with mechanisms to securely distribute security keys. Such systems can provide robust protection with minimum configuration by the user. Various encryption key manipulating algorithms have also been implemented to make it more difficult to determine the key or the encryption sequence generated from the key.
A need exists for a method of improving the security of a wireless transmission. Such a method should provide a user with the ability to determine the approximate distance to the devices capable of receiving the transmission. Then the system should provide the user with the ability to select the devices to communicate with before any communications path is established.